Air pressure controlled loose plate detector



Dec. 26, 1961 w. B. cocKs 3,014,422

2& a! M/M ATTORNEYS.

United States Patent Office 3,914,422 Patented Dec. 26, 1361 3,014,422 AIR PRESURJE CONTROLLED LOGSE PLATE DETEQTGR Walter B. (locks, Des Moines, Iowa, assignor to Meredith Publishing Company, a corporation of Iowa Filed July 18, 1960, Ser. No. 43,570 6 Claims. (@l. 101-447) but also to the operating personnel for such presses.

This failure usually takes the form of a cracking of the plate during the printing operation or of the shearing ot the plate lead base by the clamping hooks during the printing operation. In either case, the entire plate, or a portion thereof, may be thrown outwardly from the press cylinder with great force.

Various protective devices have been devised in the prior art to stop the operation of the printing press in the event of plate failure. Some of the known devices have proved to be slow acting in their operation and therefore, have not been entirely satisfactory for use with modern high speed presses. A fast acting, electronic loose plate detector suitable for high speed presses is disclosed in the patent to Wilfred H. Stone, Patent No. 2,902,929, granted September 8, 1959 and assigned to Meredith Publishing Company of Des Moines, Iowa.

Further, it often is desirable to detect other displaced material projecting above the normal surface contour of a printing press cylinder. Such displaced material for example, may take the form of displaced paper, dried portions of ink and other like material.

It is a general object of this invention to provide a fast acting pneumatic loose plate detector suitable for use with high speed rotary presses.

It is a more specific object of this invention to provide be utilized in closely space-d relationship with the printing plate of high speed rotary printing apparatus for step ping the printing press operation upon detection of a loose printing plate or other displaced material projecting above the normal surface contour of a printing plate cylinder.

In accordance with the featuresof one specific embodiment of this invention, one or more pneumatic detectors are positioned adjacent each printing plate with only a minimum working clearance therebetween. Each detector is connected in a pneumatic circuit including a source of differential air pressure, an air pressure regulator, a

pressure switch, and suitable indicating gauge and indi 'ating light means.

Advantageously, each pneumatic detector comprises avalve body having a sensitive elongated valve stem positioned for side and upward movement therein. When the printing plate is properly positioned and clamped to the press cylinder, the valve stem is biased to its outermost position, as by a spring or other resilient means acting in combination with the differential air pressure in the pneumatic circuit. In this position, the valve stem serves to close air venting ports provided in the valve body under the head of thevalve stem to prevent any venting of the diiferential pressure to the atmosphere. In this way, the air pressure in the pneumatic circuit normally is maintained at a desired differential value and the pressure switch in the circuit remains unoperated.

If and when one of the printing plates becomes loose I highly novel pneumatic valve detector means adapted to on the press cylinder and leaves the cylinder by an amount equal to the small working clearance between the clamped plate and the detector to thereby strike the exposed end of the valve stem, the air venting ports are opened and the line pressure is leaked to atmosphere. This drops the pressure in the pneumatic circuit line and activates the pressure switch to interrupt the emergency circuit and stop the printing press. The presence of any other displaced material projecting above the normal surface contour of the press cylinder is detected in a similar manner to stop the printing press operation.

Accordingly, it is another object of this invention to provide a novel displaced material detector for use with a printing press which comprises a pneumatic circuit including detector valve means connected to a source of differential air pressure and to a pressure switch such that the striking of the detector valve means by a displaced article vents the pressure line to actuate the pressure switch and stop the printing press.

It is still another object of this invention to provide a novel loose plate detector, as above, having unique and highly advantageous pneumatic valve means comprising a valve body, a movable valve stem within said body having one end extending from said body into closely spaced relationship with a properly clamped plate upon the press cylinder such that any loosening of the plate moves the valve stem to actuate a pressure switch and stop the operation of the printing press.

It is a further object of this invention to provide a new and improved displaced material detector for a printing press which is characterized by its sensitivity, its reliability of operation, and its low cost of construction and operation.

The above and other novel features which are characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view of one illustrative embodiment of pneumatic displaced material detection apparatus in accordance with the invention, and

FIGURE 2 is a cross-sectional view of one preferred construction of pneumatic valve detection means embodying the invention.

Referring now to the drawings, and more particularly to FIGURE 1 thereof, there is illustrated one particular embodiment of the invention in operative position with respect to a printing press plate. As shown, a printing plate It) is clamped to a rotatable plate cylinder 12 in the normal fashion in operative relation to the rotatable impression cylinder 14 positioned adajacent the cylinder 12.

Those skilled in the art will appreciate that certain dangers to the equipment and the operating personnel may arise if the plate 10 becomes loose from the cylinder 12 during the rotation thereof, and that these dangers have become greater with the high speed presses being used in printing plants today. In order to detect such a loosening of the plate 10 upon the cylinder 12 and to stop the printing press before any harm can be inflicted, the present invention is provided adjacent the plate 10 for immediate operation upon detection of this dangerous condition.

In accordance with the features of this invention, a plurality of pneumatic valve loose plate detectors 16 are supportingly mounted on a suitable support means, such as the rack 18 immediately above the printing plate 10. As explained in greater detail hereinbelow, each pneumatic valve 16 is provided with a movable valve stem that serves to control the operation of a pneumatic switch in the event the plate becomes loose in the cylinder 12 and comes into contact with the valve stem.

Each pneumatic valve is furnished with regulated air, such as air pressure at 10 pounds per square inch, from an air line which is coupled to a main air conduit 22. The main air conduit 22 is connected to a suitable source of air pressure at its inlet end 24 and a suitable regulator 26 may be provided to regulate the air pressure in the air line 20. As shown in FIGURE 1, the regulator 26 has a manually adjustable valve member 28 and a pres sure indicating gauge 30 to enable the air pressure in air line 20 to be adjusted to the desired value.

The main air conduit 22 also has coupled thereto a line gauge 32 suitable for testing the pressure in the air line 21 A pressure switch 34, which may include a pressure responsive diaphragm and electrical switch contacts operated thereby as well known in the art, is coupled to the main air conduit 22 such that the dropping of the pressure in the air line 20 as a result of the actuation of a pneumatic valve 16 causes the electrical switch circuitry within the pressure switch 34 to be actuatcd and close an alarm circuit to stop the rotation of the printing press cylinder. As the details of the pressure switch 34 and the alarm circuitry responsive thereto are well-known in the art, such details do not form a specific part of the present invention and it is not necessary to provide any further description of these components.

The structural details of one preferable embodiment of pneumatic valve 16 is shown in FIGURE 2 of the drawing. Advantageously, the pneumatic valve 16 comprises a valve body 40 which is externally threaded at its lower end to enable the valve body to be secured to an internally threaded opening in the support rack 18. The relative spacing between valve body 40 and the printing plate 10 can be adjusted, as desired, by rotating the valve body 40 in or out of the support rack 18 and the valve body 48 may be locked into position by means of the jam nut 42 which can be tightened upon the support rack 18.

The valve body 40 is provided with an internally threaded opening at its upper end which is adapted to receive a valve bonnet 44 therein to define a hollow pressure chamber 46 within the valve body 40. A valve head member 48 is threadedly fastened within the valve bonnet 44 and is held in position therein by means of the lock nut 50 which is tightened against the valve bonnet 44 after the valve head member 48 is properly positioned therein.

The valve head member 48 is provided with an internal air conduit 52 which is placed in air communication with the air line 20. The air conduit 52 is connected to an air passageway 54 which extends axially within the valve head member to permit the air pressure which passes from the air line 20 and the air conduit 52 to pass into the internal pressure chamber 46, in the manner indicated by the arrow 56. Normally, the chamber 46 is sealed to prevent the escape of the air pressure therein, as by means of the O-ring 58 and by means of the valve stem 60 normally positioned at the lower end of the pressure chamber 46.

The valve stem 60 is comprised of an elongated plunger 62, which is movably supported within an elongated axial bore 64 in the valve body 40, and an enlarged stem head 66 at the upper portion of the valve stem. The enlarged stem head 66 advantageously may be formed with a recessed portion 68 at the top central portion thereof so that a resilient bias member, such as the spring 70, may be positioned between the valve bonnet 44 and the valve stem 60 to normally urge the latter downwardly for sealing the pressure chamber 46.

It can be seen that the enlarged stern head 66, when the valve stem 60 is in normal position, serves to close a plurality of air exhaust ports 72 provided in the valve body 40. It further can be seen that the plunger 62 of valve stem 60 is formed with a smaller cross-section than the valve body bore 64 so that the valve stem is freely movable in both an axial direction and in a side or transverse direction within the bore, thereby making the stem very sensitive to contact with the plate 10 should the latter leave the surface of the cylinder 12.

In the normal operation of the pneumatic valve loose plate detector, the valve body 40 is adjusted in the support rack 18 so as to provide a minimum working clearance between the end of the valve stem 69 and the surface of the printing plate 10. Regulated air under pressure is admitted to the system by means of the air line 20 and the air pressure within the pressure chamber 46 of each valve 16, together with the operation of the bias spring 70, serves to maintain the valve stem 60 in its outermost position to thereby seal the pressure chamber 46 and prevent any venting of the air pressure to atmosphere. Under these conditions, the regulated pressure in the air line 20 is maintained and the pressure switch 34 will not be actuated.

If and when a printing plate 10 becomes defective and leaves the surface of the cylinder 12, the printing plate strikes the extreme end of one or more of the valve stems 60 of the pneumatic valves 16. Each valve stem 60 contacted by the loose printing plate 10 is moved sulficiently to open its exhaust ports 72 and thereby enable the pressure to be vented to atmosphere. This release of air pressure, even in small amounts, decreases the pressure activating the pressure switch 34 with the result that the switch circuitry therein is closed to energize the alarm circuit and stop the printing press.

While five pneumatic valve detectors 16 are shown in FIGURE 1 above the plate 10 as merely illustrative of one embodiment of the invention, it will be obvious to those skilled in the art that a fewer or greater number of valve detectors may be utilized with equally advantageous results. Further, it will be appreciated that, if desired, an indicator light may be associated with each pressure switch 34, which indicator light will be energized and remain on until reset after each actuation of the pressure switch.

In actual working embodiments of the present invention, tests have shown that a printing press may be stopped a number of times without any noticeable damage to the printing plate. Further, it was found that the working clearance between the valve stem 60 and the printing plate can be adjusted to plus or minus .001 inch, and in fact, a .015 inch working clearance has been found quite satisfactory for the modern-day high speed presses now in use. This working clearance manifestly may be adjusted by loosening the jam nut 42 and the lock nut 50, and by turning the valve body 40 to increase or decrease the desired working clearance.

While the invention has been particularly illustrated and described as operated by a loose plate upon a printing press cylinder, those skilled in the art will appreciate that the sensitivity of the invention is such as to permit its use with other displaced materials projecting above the normal surface contour of the press cylinder as for example, displaced paper, dried portions of ink and the like.

While there has been shown and described a specific illustrative embodiment of the invention, it Will of course, be understood that various modifications and alternative constructions may be made without departing from the true spirit and scope of the invention. Therefore, it is intended to cover by the appended claims all such modifications and alternative constructions as found within their true spirit and scope.

What is claimed as the invention is:

1. The improvement of pneumatic means for stopping the rotation of a printing press cylinder upon the detection of displaced material projecting above the normal contour of the cylinder surface comprising a rotatable printing press cylinder, a printing plate positioned on said cylinder for rotation therewith, pneumatic valve means positioned adjacent said printing plate, said pneumatic valve means comprising a valve body mounted in relatively fixed position adjacent said printing plate, an elongated valve stem disposed within said valve body, a source of differential pressure in communication with said valve body, pneumatic switching means com-municating with said source of differential pressure and valve stem, and air venting means formed in said valve body and normally closed from said source of diiferential pressure by said valve stem when said material is in normal operating position and opened to vent the source of differential pressure to atmosphere when said valve stem is moved from its normal position by material projecting above the normal contour of said cylinder.

2. The improvement of pneumatic means for stopping the rotation of a printing press cylinder upon the detection of displaced material projecting above the normal contour of the cylinder surface comprising a rotatable printing press cylinder having a printing plate positioned thereon, pneumatic valve means positioned adjacent said printing plate, said pneumatic valve means comprising a valve body and an elongated valve stem siida bly supported by said valve body, a source of differential pressure in air communication with said valve body, venting means formed in said valve body and normally closed from said source of differential pressure by said valve stem when properly placed material is positioned on said cylinder and opened to vent the source of differential pressure when said valve stem is moved from its normal position by the presence of any undesired material projecting above the normal contour of the cylinder surface and pneumatic switching means communicating with said source of differential pressure and said valve stem for stopping the rotation of the printing press cylinder when said valve stem is moved from its normal position.

3. The improvement of pneumatic means for detecting an undesirable condition with respect to a printing press cylinder comprising a rotatable printing press cylinder having a printing plate positioned thereon, pneumatic valve means positioned adjacent said printing plate, a

source of differential pressure in communication with said pneumatic valve means, pneumatic switching means communicating with said source of differential pressure and said valve means, and venting means formed in said valve means and normally closed from said source of differential pressure when said undesirable condition does not exist relative to said cylinder and opened to vent the source of pressure when said valve is actuated from its normal position as a result of said undesirable condition, whereby said switching means is operated to stop the rotation of said press cylinder.

4. The improvement of pneumatic means for stopping the rotation of a printing press cylinder upon the detection of any displaced material projecting therefrom comprising a rotatable printing press cylinder, a printing plate positioned on said cylinder for rotation therewith, pneumatic valve means comprising a valve body mounted adjacent said printing plate and including an elongated valve stem movably disposed within said valve body, a source of differential pressure in air communication with said valve body, pressure venting means formed in said valve body and normally closed from said source of differential pressure by said valve stem when no displaced material projects from the normal surface contour of said cylinder and opened to vent the source of differential pressure when said valve stem is moved from its normal position by displaced material projecting from the normal surface contour of said cylinder and pneumatic switching means communicating with said source of diiferential pressure and said valve stem for stopping the rotation or" the printing press cylinder when said valve stem is moved from its normal position.

5. The improvement of pneumatic means in accordance with claim 4 further comprising resilient biasing means positioned within said valve body in operative association with said valve stem to urge said valve stem into sealing relationship with said pressure venting means, said biasing means serving to prevent said differential pressure from being vented except when displaced material projects from the surface contour of the cylinder and engages said valve stem to cause it to move and vent said differential pressure.

6. The improvement of pneumatic means for stopping the rotation of a printing press cylinder upon the detection of displaced material thereon comprising a rotatable printing press cylinder, a printing plate positioned on said cylinder for rotation therewith, an elongated support rack positioned adjacent said printing plate and extending parallel to the axis of said cylinder, a plurality of pneumatic valve means supportingly spaced on said rack, each of said valve means comprising an elongated movable valve stem with one end closely adjacent said printing plate, a source of differential pressure in communication with each of said valve means, pneumatic switching means communicating with said source of differential pressure and said valve means, and pressure venting means formed in each of said valve means and normally closed from said source of differential pressure by the valve stem when a properly placed material is on said cylinder and opened by the movement of the valve stem to vent the source of differential pressure to atmosphere when displaced material projects from the normal surface contour of said cylinder to engage one or more of said valve stems.

No references cited. 

